Shower deck



Sept. 5, 1944. P. LAMBERT SHOWER DECK Filed June 21, 1941 ATI'OR YPatented Sept. 5, 1944 SHOWER DECK Pierre Lambert, New Rochelle, N. Y.,assignor to The Lummus Company, New York, N. Y., a corporation ofDelaware Application June 21, 1941, Serial No. 399,137

3 Claims.

The present invention relates to improvements in fractionating showerdecks for a distillation column and more particularly to such showerdecks employed in the rectification of petroleum vapors under vacuum.

In some types of fractionating operations, it is the practice to carryout the fractionation in a column provided with a plurality of showerdecks, each of which comprises an imperforate liquid collecting section,upon which the downflowing reflux liquid from the deck above iscollected, and a perforated shower-forming section, which showers thereflux liquid onto the deck below.

Each deck extends partially across the column,

and the respective decks are so arranged that alternate decks overlapone another whereby the ascending vapors are forced to follow a zigzagpath in their upward passage through the column. The function of theperforated section is to provide such a shower as will insure anintimate contact between the downflowing reflux liquid and the ascendingvapors, which pass horizontally through the shower from each deck.

Such a shower deck is customarily provided with a weir, which separatesthe imperforate sectionfrom the perforated section. The liquid LII whichis collected on the imperforate section builds up behind this weir, andits depth will depend on the height of the weir and on the head ofreflux liquid flowing over the weir. In such operation, it will beapparent that the liquid which is collected on the deck will be held upor retained thereon in a more or less' static condition for a certainlength of time before it passes over the weir.

This holdup time of the reflux liquid on a shower deck is determined bythe size of he liquid pool that forms behind the weir and by the rate offlow of reflux downwardly through the column. It will thus beappreciated that, the longer the holdup time is, the longer the refluxliquid collected on a shower deck is subjected to the operatingtemperatures. Where the material undergoing fractionation is a petroleumoil such as a high boiling lubricating oil, this consideration becomesimportant inasmuch as such an oil is subject to cracking or otherdeterioration at the high fractionating temperatures employed. It isdesirable, therefore, to reduce the holdup time to a minimum in order toavoid cracking or deterioration of the oil at high op-' eratingtemperatures.

Although various constructions and arrangements of shower decks and thelike have .been proposed heretofore to accomplish an intimate contactbetween downflowing reflux liquid in shower form and rising vapors, tomy knowledge none of these have contemplated reducing the holdup time ofthe liquid flowing across the decks by lowering of the amount of staticliquid col-- lected thereon.

The principal object of this'invention isthe provision of afractionating shower deck designed to reduce materially the holdup timeof the reflux liquid collected thereon whereby the time during which theliquid is subjected to the operating temperature is reduced to aminimum.

Another object of the invention is the provision of a shower deckconstruction for use in the fractionation of hydrocarbon oils wherebythe-quantity of reflux collected on the deck is reduced to a minimum andcracking or deterioration of the oils because of subjection to highoperating temperatures can be avoided. 7

Other objects of the invention are features of construction which willmanifest themselves as the description proceeds.

In accordance with the present invention, I provide an improvedfractionating shower deck which is especially adapted for vacuumdistillation of high boiling petroleum oils. The shower deck is sodesigned that the imperforate reflux collecting section thereof slopesdownwardly and inwardly towards the perforated shower-forming section.liquid collected on the shower deck is reduced to a minimum, andcracking or decomposition of the oil atthe requisite high fractionatingtemperatures can be substantially avoided. At the same time, a completeshower of liquid across the path of the vapors is also provided.

Inthe accompanying drawing,

Fig. l is a fragmentary elevation partly in section of a columnembodying one form of the improved shower deck, which section is takenon line l-I of Fig. 2;

Fig. 2 is a horizontal sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a vertical sectional view of a modified form of thefractionating shower deck showing weir means for controllingthe...formation of the shower; and

Fig. 4 is a vertical sectional view of another modified form of theshower deck having means for controlling the formation of the shower.

Referring to Figs. 1 and 2 of the drawing, I have shown a column,indicated generally by the reference character I, which comprises ashell 2 and which is adapted for the rectification of high boilingpetroleum vapors under vacuum.

In this manner the amount of reflux- The oil to be fractionated isvaporized in any suitable still, and the vapors are admitted to theshell 2 in any well known manner. The shell 2 is provided with aplurality ofrectifying or a contact zones, in each of which is located afractionating shower deck 3 partially extending transversely across theshell. The fractionatin! decks 3 are alternately arranged in the shellas must first fill the space between weirs i and it before covering afurther portion of perforated section 5. Thus, a complete shower isalways provided. Although weirs I4 and I! are shown to havegthe sameheight. the height of'the weirs may be increased progressively from weir8 to weir 9, or any other suitable arrangement may be employed.

In the modification shown in Fig. 4, the shower deck is provided with.the perforated showerforming section B sloping downwardly toward the sothat a continuous countercurrent reflux action is obtained.

In accordance with my invention, the shower deck 3 comprises an inclinedimperforate liquid collecting section I and a perforated showerformingsection 5. The shower-forming section is provided with a large number ofslits, holes, or

perforations of small diameter as shown so that,

when the reflux liquid passes therethrough, it forms a shower of finestreams. Preferably these two sections are separated by a weir 6, whichprovides for an even distribution of the reflux liquid as it flows ontothe shower-forming section. The height of weir 6 is preferably made assmall as possible so that the amount of liquid collected behind it onthe imperforate section 4 may be reduced to a minimum. If desired, theupper edge of weir 6 may be serrated. An end dam or weir 9 is alsoprovided to retain the reflux liquid on the shower-forming section 5.

The angle at which the imperforate collecting section 4 is inclineddownwardly and inwardly from the column wall and the height of the weir6 determine the amount or quantity of static liquid retained on thecollecting: section of each shower deck. By designing the. shower deck 3for the desired fractionating operation I can thus reduce the holduptime of the reflux liquid collected on the imperforate section 4 to aminimum for any particular operating conditions and can thereby avoiddeterioration of the liquid material at the operating temperatures.Particularly in the distillation of high boiling petroleum oils such aslubricating oils is the duration of this holdup time an important factorinasmuch as the oils must necessarily be fractionated at hightemperatures with the consequent possibility of cracking ordecomposition of the oils when maintained at such temperatures for anysustained period of time.

.Where it is desired to remove a side stream from column I, weir B maybe increased in height soas to form a pool ll of reflux liquidsuiilcient to permit withdrawal of aside stream from. the particulardeck and at the same time to provide a flow of liquid over the weir ontoshower-forming section 5. A suitable draw-off I2 is provided for thewithdrawal of the side stream from the collecting section-4 through thecolumn wall.

With reference to Fig. 3, it will be noted that I have provided theshower section 5 with a plurality of weirs as at M and If. These weirsserve to-control the formation of the shower and insure that a completeshower is presented transversely across the path of flow of the vaporsirrespective of the rate of reflux flow. It will be appreciated that,with this construction, when the rate of reflux flow is low, the liquidflowing over weir 6 oppositely inclined imperforate section 4. Thisconstruction also insures the presentation of a complete showertransversely across the path of vapor flow. When the rate of flow ofreflux is low, the liquid flowing over weir i must, of necessity, passthrough the lowermost row of holes in section 5. The holes may all bemade the same size,

but it is preferable to gradually increase the diameter of the holes inaccordance with the distance from. weir 8. If found desirable, thespacing between the several rows of perforations may also be varied. Itwill also be apparent that a minimum of liquid passing over the weir Iwill assure a complete shower of liquid across the column with thisconstruction because of the slope of the perforated section whether ornot Y the imperforate section is also inclined.

Although reference has been made particularly to vacuum distillation ofhigh boiling petroleum hydrocarbons, for which operation the inventionhas special advantages, it will be apparent that the invention is alsoapplicable to the distillation of other materials which are subject todecomposition under subjection to similar conditions for the particularmaterials.

Although the shower-forming section 5 of the shower deck of Figs. 1 and2 is shown to be in the form of a trough attached to the lower edge' ofthe inclined imperforate section 4, it will be appreciated that theconstruction may be such that section 5 is flush with the lower edge ofsection 4. A similar flush construction may be used in the modified formof shower deck shown in Fig. 4.

Various modifications of the invention will suggest themselves to thoseskilled in the art, but it is desired that all such modifications arewithin the spirit of the invention as come within the scope of theappended claims.

I claim:

1. In combination with a column for contact of rising vapors withfalling liquid, an upper shower deck and a lower shower deck invertically spaced relation to each other within the column and eachextending only partially across the interior of the column andcomprising an imperforate liquid-collecting section constructed andarranged with the upper surface thereof downwardly inclined continuouslyin .vertical section and a'trough-lik shower section extending along thelower edge of said liquid-collecting section and having its bottomformed with numerous small perforations distributed therealong andthereacross, said a weir between said sections and extending upwardlyfrom said liquid-collecting section at the lowest level of the uppersurface of the latter to a level below the uppermost level oftion of theupper deck disposed to discharge liquid upon the imperforateliquid-collecting section only of the lower deck.

2. In combination with a column for contact of rising vapors withfalling liquid, an upper shower deck and a lower shower deck invertically spaced relation to each other within the column and eachextending only partially across the interior of the column andcomprising an imperforate liquid-collecting section constructed andarranged with the upper surface thereof downwardly inclined continuouslyin vertical section 3. In combination with a column for contact ofrising vapors with falling liquid, an upper shower deck and a lowershower deck in vertically spaced relation to each other within thecolumn and each extending only partially across the interior of thcolumn and comprising an imperforate liquid-collecting sectionconstructed and arranged with the upper surface thereof down- "wardlyinclined continuously in vertical section and a trough-like showersection extending along the lower edge of said liquid-collecting sectionand having its bottom transversely inclined reversely to the directionof inclination of said surface of the liquid-collecting section andformed with numerous small perforations distributed therealong andthereacross, and a weir between said sections and extending upwardlyfrom said liquid-collecting section at the lowest level of the uppersurface of the latter to a level below the uppermost level of saidsurface and constructed and arranged for evenly distributed overflow ofliquid from the liquid-collecting section to the shower section and forvretention of a relatively small volume of liquid upon the collectingsection, said decks being constructed and arranged in a staggeredrelation to each other with the shower section of the upper deckdisposed to discharge liquid upon the imperforate liquidcollectingsection only of the lower deck.

in a staggered relation to each other with the shower section of theupper deck disposed to discharge liquid upon the imperiorateliquidcollecting section only of the lower deck, and a side-streamconduit connected to the liquid-collecting section oiyone of said decksand leading from a low point of the upper surface of the latterdownwardly and outwardly through the wall of the column.

' PIERRE LAMBERT.

